As a former Greenpeace insider, Patrick Moore wasn’t surprised by the heated reaction from the left on his explosive testimony about climate change last week before a Senate committee.

Mr. Moore drew headlines for disputing the environmental movement’s doomsday scenario, depicting climate change over the past century as “minor warming” and arguing that “there is no scientific proof that human emissions of carbon dioxide are the dominant cause.”

As a result, Mr. Moore came under fire for “climate denial” from the liberal group Media Matters for America. He has been persona non grata at Greenpeace for years.

Mr. Moore dismisses such criticism as an “ad hominem personal attack that doesn’t have anything to do with the subject at hand.” At the same time, he doesn’t mind taking a swipe at those who advocate drastic emissions reductions in the name of stopping climate change.

“I describe the climate change movement as a combination of an extreme political ideology and a religious cult all rolled into one,” said Mr. Moore. “It’s a very, very dangerous social phenomenon. It causes them to think they have the right to dictate what we do.”

The Canadian ecologist has long been a thorn in the side of Greenpeace, which carries two statements on its website disputing his credentials as an environmentalist.

“While it is true that Patrick Moore was a member of Greenpeace in the 1970s, in 1986 he abruptly turned his back on the very issues he once passionately defended,” says a Greenpeace statement. “He claims he ‘saw the light’ but what Moore really saw was an opportunity for financial gain.”

Mr. Moore often is described as a Greenpeace co-founder, which Greenpeace officials dispute, but it’s safe to say that he was there almost from the start. The group that became Greenpeace was founded in 1970; Mr. Moore joined a year later and quickly assumed a leadership role.

“I don’t claim that has necessarily any overwhelming importance, whether I was a founder or not, but the fact is I was there at the beginning, even before it was called Greenpeace,” said Mr. Moore. “I was on the first voyage, and I played a very central role in the organization for 15 years.”

He said he left because he was alarmed by the shift in the organization’s goals. Greenpeace was originally about saving the environment and ending the threat of nuclear war. Over time, he said, the “green” overtook the “peace.”

“By the time I left in ‘86, Greenpeace had drifted into a position of characterizing humans as the enemies of the Earth, a cancer on the planet,” said Mr. Moore. “One of my main contentions is that to see humans as separate from nature and the ecology and the environment is defying the most important first law of ecology, which is that we are all part of nature.”

Teaching children that “the human species is a separate, evil thing from nature is extremely damaging to their orientation of life,” he said.

He said environmentalists have attempted to discredit him because his remarks are devastating to the climate change movement. The path to significantly lowered emissions in the name of combating climate change leads to some alarming places, he said, namely a world with greater poverty and less democracy.

The climate change argument “gives them an overarching policy framework to dictate human civilization,” said Mr. Moore. “It basically allows them to say what the energy policy should be, which is the key policy underlying the whole of modern civilization.”

He cited the environmental group 350.org, which is named for the goal of reducing atmospheric carbon dioxide by more than 20 percent to 350 parts per million.